Mitochondrial dysfunction is one of the early features in Alzheimer's disease (AD) affected brain. Recent studies have highlighted the role of mitochondrial A in AD pathogenesis. A progressively accumulates in the mitochondria of AD brain and transgenic mutant amyloid precursor protein (mAPP) mice overexpressing A, which is linked to mitochondrial and neuronal malfunction in AD. Thus, accumulation of A in mitochondria may be an initiating pathological event leading to mitochondrial and neuronal perturbation. PreP, mitochondrial peptidasome, is the novel mitochondrial peptidase responsible for degrading presequences and other short unstructured peptides in mitochondria. Human PreP homologue, hPreP, located in brain mitochondria, is capable of degrading A in vitro, suggesting that hPreP may potentially be of importance in preventing amyloid pathology of Alzheimer disease through its degradation and clearance of mitochondrial A. So far, it is unknown whether PreP is ultimately implicated in causing AD: whether PreP activity is altered in Alzheimer's disease brain and whether PreP activity plays a key role in mitochondrial A accumulation. In this R21 exploratory/developmental research proposal, we will investigate whether alterations in PreP modification, expression and its enzyme activity occur in the AD brains and whether levels of PreP expression and activity are correlated to the accumulation of mitochondrial A and amyloid pathology. Furthermore, we will examine the effect of A and oxidative stress on PreP activity and to determine whether PreP activity contributes to the accumulation of mitochondrial A using in vitro neuronal culture model. The goal of this proposal is to determine the significance of PreP in the AD pathogenesis, focusing on expression/activity of PreP, mitochondrial A accumulation, oxidative stress, and mitochondrial function, utilizing well-controlled AD and non-AD brains, transgenic AD mice overexpressing A, and novel genetically manipulated neuron culture (gaining/losing PreP function). The outcomes of the studies will have a major impact on the amyloid pathology in the AD field. PUBLIC HEALTH RELEVANCE: The goal of this project is to investigate whether alternations in PreP expression and enzyme activity occur in the AD brains associated with accumulation of mitochondrial A and amyloid pathology, to assess the effect of PreP activity on A accumulation in mitochondria and mitochondrial/neuronal function, and to create novel neuronal cell lines with altered PreP levels and enzymatic activity. The outcomes of the proposed studies will have a major impact in the field of AD and aging particular.